/***
 * ASM: a very small and fast Java bytecode manipulation framework
 * Copyright (c) 2000-2007 INRIA, France Telecom
 * All rights reserved.
 */
package org.rsbot.loader.asm;

/**
 * A non standard class, field, method or code attribute.
 *
 * @author Eric Bruneton
 * @author Eugene Kuleshov
 */
public class Attribute {

	/**
	 * The type of this attribute.
	 */
	public final String type;

	/**
	 * The raw value of this attribute, used only for unknown attributes.
	 */
	byte[] value;

	/**
	 * The next attribute in this attribute list. May be <tt>null</tt>.
	 */
	Attribute next;

	/**
	 * Constructs a new empty attribute.
	 *
	 * @param type the type of the attribute.
	 */
	protected Attribute(final String type) {
		this.type = type;
	}

	/**
	 * Returns <tt>true</tt> if this type of attribute is unknown. The default
	 * implementation of this method always returns <tt>true</tt>.
	 *
	 * @return <tt>true</tt> if this type of attribute is unknown.
	 */
	public boolean isUnknown() {
		return true;
	}

	/**
	 * Returns <tt>true</tt> if this type of attribute is a code attribute.
	 *
	 * @return <tt>true</tt> if this type of attribute is a code attribute.
	 */
	public boolean isCodeAttribute() {
		return false;
	}

	/**
	 * Returns the labels corresponding to this attribute.
	 *
	 * @return the labels corresponding to this attribute, or <tt>null</tt> if
	 *         this attribute is not a code attribute that contains labels.
	 */
	protected Label[] getLabels() {
		return null;
	}

	/**
	 * Reads a {@link #type type} attribute. This method must return a <i>new</i>
	 * {@link Attribute} object, of type {@link #type type}, corresponding to
	 * the <tt>len</tt> bytes starting at the given offset, in the given class
	 * reader.
	 *
	 * @param cr      the class that contains the attribute to be read.
	 * @param off     index of the first byte of the attribute's content in {@link
	 *                ClassReader#b cr.b}. The 6 attribute header bytes, containing the
	 *                type and the length of the attribute, are not taken into account
	 *                here.
	 * @param len     the length of the attribute's content.
	 * @param buf     buffer to be used to call
	 *                {@link ClassReader#readUTF8 readUTF8},
	 *                {@link ClassReader#readClass(int, char[]) readClass} or
	 *                {@link ClassReader#readConst readConst}.
	 * @param codeOff index of the first byte of code's attribute content in
	 *                {@link ClassReader#b cr.b}, or -1 if the attribute to be read is
	 *                not a code attribute. The 6 attribute header bytes, containing the
	 *                type and the length of the attribute, are not taken into account
	 *                here.
	 * @param labels  the labels of the method's code, or <tt>null</tt> if the
	 *                attribute to be read is not a code attribute.
	 * @return a <i>new</i> {@link Attribute} object corresponding to the given
	 *         bytes.
	 */
	protected Attribute read(
			final ClassReader cr,
			final int off,
			final int len,
			final char[] buf,
			final int codeOff,
			final Label[] labels) {
		final Attribute attr = new Attribute(type);
		attr.value = new byte[len];
		System.arraycopy(cr.b, off, attr.value, 0, len);
		return attr;
	}

	/**
	 * Returns the byte array form of this attribute.
	 *
	 * @param cw        the class to which this attribute must be added. This parameter
	 *                  can be used to add to the constant pool of this class the items
	 *                  that corresponds to this attribute.
	 * @param code      the bytecode of the method corresponding to this code
	 *                  attribute, or <tt>null</tt> if this attribute is not a code
	 *                  attributes.
	 * @param len       the length of the bytecode of the method corresponding to this
	 *                  code attribute, or <tt>null</tt> if this attribute is not a code
	 *                  attribute.
	 * @param maxStack  the maximum stack size of the method corresponding to
	 *                  this code attribute, or -1 if this attribute is not a code
	 *                  attribute.
	 * @param maxLocals the maximum number of local variables of the method
	 *                  corresponding to this code attribute, or -1 if this attribute is
	 *                  not a code attribute.
	 * @return the byte array form of this attribute.
	 */
	protected ByteVector write(
			final ClassWriter cw,
			final byte[] code,
			final int len,
			final int maxStack,
			final int maxLocals) {
		final ByteVector v = new ByteVector();
		v.data = value;
		v.length = value.length;
		return v;
	}

	/**
	 * Returns the length of the attribute list that begins with this attribute.
	 *
	 * @return the length of the attribute list that begins with this attribute.
	 */
	final int getCount() {
		int count = 0;
		Attribute attr = this;
		while (attr != null) {
			count += 1;
			attr = attr.next;
		}
		return count;
	}

	/**
	 * Returns the size of all the attributes in this attribute list.
	 *
	 * @param cw        the class writer to be used to convert the attributes into byte
	 *                  arrays, with the {@link #write write} method.
	 * @param code      the bytecode of the method corresponding to these code
	 *                  attributes, or <tt>null</tt> if these attributes are not code
	 *                  attributes.
	 * @param len       the length of the bytecode of the method corresponding to
	 *                  these code attributes, or <tt>null</tt> if these attributes are
	 *                  not code attributes.
	 * @param maxStack  the maximum stack size of the method corresponding to
	 *                  these code attributes, or -1 if these attributes are not code
	 *                  attributes.
	 * @param maxLocals the maximum number of local variables of the method
	 *                  corresponding to these code attributes, or -1 if these attributes
	 *                  are not code attributes.
	 * @return the size of all the attributes in this attribute list. This size
	 *         includes the size of the attribute headers.
	 */
	final int getSize(
			final ClassWriter cw,
			final byte[] code,
			final int len,
			final int maxStack,
			final int maxLocals) {
		Attribute attr = this;
		int size = 0;
		while (attr != null) {
			cw.newUTF8(attr.type);
			size += attr.write(cw, code, len, maxStack, maxLocals).length + 6;
			attr = attr.next;
		}
		return size;
	}

	/**
	 * Writes all the attributes of this attribute list in the given byte
	 * vector.
	 *
	 * @param cw        the class writer to be used to convert the attributes into byte
	 *                  arrays, with the {@link #write write} method.
	 * @param code      the bytecode of the method corresponding to these code
	 *                  attributes, or <tt>null</tt> if these attributes are not code
	 *                  attributes.
	 * @param len       the length of the bytecode of the method corresponding to
	 *                  these code attributes, or <tt>null</tt> if these attributes are
	 *                  not code attributes.
	 * @param maxStack  the maximum stack size of the method corresponding to
	 *                  these code attributes, or -1 if these attributes are not code
	 *                  attributes.
	 * @param maxLocals the maximum number of local variables of the method
	 *                  corresponding to these code attributes, or -1 if these attributes
	 *                  are not code attributes.
	 * @param out       where the attributes must be written.
	 */
	final void put(
			final ClassWriter cw,
			final byte[] code,
			final int len,
			final int maxStack,
			final int maxLocals,
			final ByteVector out) {
		Attribute attr = this;
		while (attr != null) {
			final ByteVector b = attr.write(cw, code, len, maxStack, maxLocals);
			out.putShort(cw.newUTF8(attr.type)).putInt(b.length);
			out.putByteArray(b.data, 0, b.length);
			attr = attr.next;
		}
	}
}
